The US has ordered all non-essential diplomatic staff to leave Tunisia and Sudan and updated its travel warning for those regions.

"Given the security situation in Tunis and Khartoum, the State Department has ordered the departure of all family members and non-emergency personnel from both posts, and issued parallel travel warnings to American citizens," State Department spokeswoman Victoria Nuland said in a statement.

Overnight, riot police stormed into Cairo's Tahrir Square and rounded up hundreds of people after four days of clashes and demands from protesters for the US ambassador to be expelled.

Saudi Arabia's highest religious authority denounced the attacks on diplomats and embassies across the Middle East as un-Islamic.

In contrast, the Yemen-based branch of Al Qaeda applauded the killings of US diplomats in Libya and urged Muslims to kill more, calling the video posted on the internet another chapter in the "crusader wars" against Islam.

A California man convicted of bank fraud, who has denied reports that he was involved in the film's production, was taken in for questioning by officers investigating possible probation violations stemming from the making of the film.

Afghanistan's Taliban claimed responsibility for an attack on a base that killed two American Marines, saying it was a response to the insults to the founder of Islam.

US president Barack Obama, leading a ceremony on Friday to honour the US ambassador to Libya and three other Americans who died in an attack on the US consulate in Benghazi on September 11, vowed to "stand fast" against the violence.

"The United States will never retreat from the world," he said.

The Pentagon rushed to bolster security at missions abroad.

Libyan authorities said they had identified 50 people who were involved in the attack in which ambassador Christopher Stevens died.

He described the short film as "miserable" and "criminal", but said attacks on the innocent and on diplomats were "a distortion of the Islamic religion and are not accepted by God".

The video, circulating on the internet under several titles including Innocence of Muslims, portrays Mohammad as a womaniser and a fool.

US man arrested

In the Los Angeles suburb of Cerritos, Nakoula Basseley Nakoula, 55, who has denied involvement in the film in a phone call to a Coptic Christian bishop, was ushered out of his home and into a waiting car by sheriff's deputies, his face shielded by a scarf, hat and sunglasses.

"He will be interviewed by federal probation officers," a police spokesman said.

"He was never put in handcuffs ... It was all voluntary."

US officials have said authorities are not investigating the film project itself, and that even if it was inflammatory or led to violence, simply producing it cannot be considered a crime in the United States, which has strong free speech laws.

A statement posted on a website used by Al Qaeda in the Arabian Peninsula on Saturday called on Muslims to "follow the example of Omar al-Mukhtar's descendants (Libyans), who killed the American ambassador".

"Let the step of kicking out the embassies be a step towards liberating Muslim countries from the American hegemony," the Yemen-based group said.

Marine reinforcements have been hastily dispatched to the US missions in Yemen and other countries since the unrest erupted. But Sudan said on Saturday it was turning down Washington's request to send more troops.

Victoria's laws for disclosing political donations have long been criticised as among the weakest in the nation, but Premier Daniel Andrews says his proposed reforms will make the state's donations laws "the strictest donation laws in the country".